The present invention is directed to multi-bed horizontal ammonia converters such as the converter described in U.S. Pat. No. 4,452,760 to Peterson et al. which is hereby incorporated herein by reference. Many of these reactors are in use operating on a magnetite catalyst. It is frequently desired to modify the Peterson et al. reactor for increased ammonia conversion.
With reference to the Peterson et al. ammonia converter shown in FIGS. 1 and 1A, the outer shell S is a cylindrical pressure vessel which includes a main body 10 having an inlet 12 and an outlet 14 at one end. A head 16 is removably attached to main body 10 and has an exchanger bypass 18. An inner shell or basket B is removably positioned within outer shell S. The inner shell B is a cylindrical vessel which is divided into sections. The end wall 20 and a first wall 22 define a heat exchange section 25 of shell B. A second wall 24 and a third wall 26 define a first catalyst section 28. A second catalyst bed section is defined between third wall 26 and the outer end wall 30 of shell B. A gas transfer section 34 is disposed between first wall 22 and second wall 24.
The synthesis gas enters the outer shell S of the Peterson et al. reactor through inlet 12. The gas is at a temperature below the desired reaction temperature, but maintains the outer shell S at low temperatures as it passes through the annular space 36 (shown enlarged in FIG. 1A) between the outer shell S and the inner shell B. Preferably, the gas is introduced through inlet 12 at one end and flows to the other end where it passes through opening 40 in end wall 20. Opening 40 is at the top of end wall 20 where the gas enters the heat exchange section 25 of inner shell B. The gas passes downwardly over a plurality of tubes 42 heating the gas to reaction temperatures. As best seen in FIG. 1A, the gas enters the bottom of gas transfer section 34 and passes to the top where it enters the first catalyst bed section 28 above the horizontal bed of catalyst. As the gas passes through the catalyst, the hydrogen and nitrogen react to form ammonia and due to the exothermic reaction, the product gases are hotter than the entering gas. The product gas contains a mixture of ammonia and unreacted hydrogen and nitrogen. The product gas passes through gas transfer section 34 where it enters the inside of tubes 42. As the product gas passes through the tubes 42 it is cooled in heat exchange section 25. The cooled product gas then re-enters gas transfer section 34 where it enters pipe 44 which extends from gas transfer section 34, through first catalyst bed section 28 and passes through openings 46 in pipe 44 above a horizontal bed of catalyst in second catalyst bed section 32. In the Peterson et al. reactor it is preferred that the second catalyst bed section 32 comprises two horizontal beds of catalyst through which the product gas from the first bed of catalyst passes. Preferably, the second catalyst bed section 32 is in two sections formed by partial wall 124 which extends above catalyst bed 122 and partial wall 126 which extends below adjacent catalyst bed 128. Further ammonia is produced in the catalyst beds 122 and 128 and again the product gas is heated. The hot reaction product gas then passes through end wall 30 through an outlet pipe 48 where it passes through outlet 14.